PubChem Chemical & BioAssay Repository

Public NIH repository at NCBI housing over 110 million unique chemical structures, substance records, and high-throughput bioassays.

Specifications & Metrics

type: Chemical Structures & BioAssays
maintainer: National Center for Biotechnology Information (NCBI), U.S. National Library of Medicine (NIH)
identifier format: CID (Compound ID), SID (Substance ID), and AID (Assay ID)
license: U.S. Government Public Domain work (freely downloadable via web UI, REST PUG API, and FTP)
introduced: 2004

Released in 2004 by the National Center for Biotechnology Information (NCBI) under the NIH Molecular Libraries Program, PubChem is organized into three linked databases: PubChem Substance (SID), PubChem Compound (CID), and PubChem BioAssay (AID).
Whereas Substance records preserve depositor-submitted descriptions from hundreds of contributing vendors and agencies, Compound records deduplicate and standardize structures into canonical connectivity, InChIKeys, and isomeric SMILES.
PubChem BioAssay archives millions of quantitative high-throughput screening readouts from the NIH Molecular Libraries Probe Production Centers Network (MLPCN) and NCATS alongside literature-curated target activity.